Method of forming a cemented carbide composition



United States Patent Ofilice 3,1514%? Patented Nov. 17, 1964 3,157,497 METHGD F FORMING A CEMENTED CAREIDE CQMPOSITKON Henry S. Spacil, Schenectady, N.Y., assignor to General Electric Company, a corporation or New York No Drawing. Filed Aug. 1, 1961, Ser. No. 128,377 4 Claims. (Cl. 75-294) This invention relates to compositions and more particularly ot improved methods of forming cemented carbide compositions and grade powders.

Presently, cemented carbides and grade powders are produced by incorporating a metallic binder such as cobalt with the carbide powder which resultant mixture is then ball-milled to distribute the binder metal to result in a grade powder. The milled powder mixture is pressed, provided optionally with a material such as paraffin, if necessary, presintered, and sintered to yield a cemented carbide. Additionally, wet milling is often employed whereby the binder is incorporated with a carbide and the resultant powder is mixed with a vehicle prior to ball-milling. Present practice requires large ball-mills which are subject to heavy wear and which contaminate the carbide and binder powders. Thus, it would be desirable to eliminate this contamination and the ball-milling step in the process.

it is an object of my invention to provide a method of forming cemented carbide articles and grade powders in which ball-milling is eliminated.

it is another object of my invention to provide a method of forming cemented carbide articles and grade powders in which the metallic binder is incorporated into the carbide as a compound of the desired binder metal.

it is a further object of my invention to provide a method of forming cemented carbide articles and grade powders in which the binder is incorporated as a metallic halide whose metal is selected from the group consisting oi iron, nickel, and cobalt.

In carrying out my invention in one form, a method of forming a grade powder comprises providing a metallic halide in which the metal is selected from the group consisting of iron, nickel, and cobalt, dissolving the metallic halide in a non-aqueous solvent having a high solubility for the metallic halide, mixing a carbide powder in the formed solution, evaporating the solvent to result in a powder, placing the powder in a reducing atmosphere, and reducing the metallic halide to the metal thereof.

These and various other objects, features and advantages of the invention will be better understood from the following description:

I found unexpectedly that a metallic binder in the form of a metallic halide having a metal selected from the group consisting of iron, nickel, and cobalt could be added to a carbide to form a cemented carbide composition or grade powder. This method eliminates conventional dry or wet ball-milling in cemented carbide or grade powder manufacturing. I found further that the metallic halide could be dissolved in a non-aqueous solvent having a high solubility for the halide and the carbide powder mixed in the formed solution. Normally, it is desirable to add 3 weight percent to 20 weight percent of metal binder to the carbide to form a cemented carbide or grade powder. The employment of the non-aqueous solvent which is free of water prevents also the problem of oxidation of the powder or of the binder metal. Subsequently, the solvent is evaporated to result in a powder with a uniform distribution of metallic halide therein. This powder is then heated in a hydrogen atmosphere to reduce the metallic halide to its respective metal without vaporizing the halide and without sintering the metal, to produce a finely divided grade powder. Such powder can then be formed into a coherent compact, if necessary, presintered, and sintered at an elevated temperature toform a cemented carbide article.

My method of forming a cemented carbide composition or grade powder includes various metallic carbides, for example, tungsten carbide, titanium carbide, tungstentitanium carbide, tungsten-tantalum carbide, tungstentitanium-tantalum carbide, hafnium carbide, molybdenum carbide and molybdenum-tantalum carbide. I found that the metallic halide should be a halide in which the metal is selected from the group consisting of iron, nickel, and cobalt. Additionally, I prefer to employ the chlorides and bromides of these metals rather than the iodides. The organic solvent should be non-aqueous with a high solubility for the halide which is employed. For example, methanol, ethanol and acetone are suitable non-aqueous solvents for use in my method.

An example of a method of forming a grade powder in accordance with the present invention is'as follows:

Thirty-five parts by weight of anhydrous cobalt chloride was added to parts of methanol, the non-aqueous solvent. Tungsten carbide powder wa mixed in the solution whereby about 9 weight percent of cobalt metal was present. The solvent was evaporated to result in a dried.

powder which was crushed to break down any lumps. The powder was then placed in boats and heated to 450 C. in hydrogen to reduce the cobalt chloride to cobalt. No appreciable vaporization of the cobalt chloride occurred at this temperature. Furthermore, this reduced temperature was low enough to prevent sintering of the reduced cobalt. After reduction, the powder provided a grade powder which wa in a finely divided state, characteristic of the original tungsten carbide powder.

An example of a method of forming a cemented carbide composition in accordance with the present invention is as follows:

T hirty-tiv'e parts by weight of anhydrous cobalt chloride was added to 80 parts of methanol, the non-aqueous solvent. Tungsten carbide powder was mixed in the solution whereby about 9 weight percent of cobalt metal was present. The solvent was evaporated to result in a dried powder which was crushed to break down any lumps. The powder was then placed in boats and heated to 450 C. in hydrogen to reduce the-cobalt chloride to cobalt. No appreciable vaporization of the cobalt chloride occurred at this temperature. Furthermore, this reduced temperature was low enough to prevent Sintering of the reduced cobalt. fter reduction, the powder provided a grade powder which was in a finely divided state, characteristic of the original tungsten carbide powder.

This resultant powder was pressed at about 15 tons per square inch to form a coherent compact that was handled readily without excessive chippage of corners. The cobalt metal in the compact was free of mechanical strain and relatively free of surface contamination by the atmosphere or of surface contamination which is normally caused by ball-milling. This compact was then sintered for one hour at 1450 C. The resultant cemented carbide article had a metallic appearance, a density of at least 14.65 grams per cubic centimeter and a typical cemented carbide microstructure.

While other modifications of this invention and variations of method which may be employed within the scope of the invention have not been described, the invention is intended to include such that may be embraced'within the following claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A method of forming a grade powder which comprises providing a metallic halide in which the metal is selected from the group consisting of iron, nickel and cobalt, dissolving said metallic halide in a non-aqueous t; organic solvent having a high solubility for said metallic halide, mixing a carbide powder in the formed solution, the non-aqueous organic solvent being free of water to prevent oxidation of the carbide powder, evaporating said solvent to result in a powder, placing said powder in a reducing atmosphere, and reducing said metallic halide to the metal thereof.

2. A method of forming a cemented carbide which comprises providing a metallic halide in which the metal is selected from the group consisting of iron, nickel and cobalt, dissolving said metallic halide in a non-aqueous organic solvent having a high solubility for said metallic halide, mixing a carbide powder in the formed solution, the non-aqueous organic solvent being free of water to prevent oxidation of the carbide powder, evaporating said solvent to result in a powder, placing said powder in a reducing atmosphere, reducing said metallic halide to the metal thereof, pressing said powder to form a coherent compact,'and sintering said compact.

3; A method of forminga grade powder which comprises providing cobalt chloride, dissolving said cobalt chloride in methanol, mixing tungsten carbide powder in the formed solution, evaporating said solvent to result in a powder, placing said powder in a reducingatrnosphere;

and reducing said cobalt chloride to cobalt.

4. A method of forming a cemented carbide which comprises providing cobalt chloride, dissolving said cobalt chloride in methanol, mixing tungsten carbide powder'in the formed solution, evaporating said solvent to'result in a powder, placing said powder in a reducing atmosphere, reducing said cobalt chloride to cobalt, pressing said powder to form a coherent compact, and sintering said compact.

References Cited by the Examiner,

- UNITED STATES PATENTS 1,775,014 9/30 Adams 75-204' 1,874,641 8/32 Sessions 75204 2,483,075 9/49 Truesdale 75-212 XR 2,853,401 9/58 Mackiw et a1 752l2 XR FOREIGN PATENTS 626,653 7/49 Great Britain.

CARL D. QUARFORTH, Primary Examiner; I

OSCAR R. VERTIZ. Examiner. 

1. A METHOD OF FORMING A GRADE POWDER WHICH COMPRISES PROVIDING A METALLIC HALIDE IN WHICH THE METAL IS SELECTED FROM THE GROUP CONSISTING OF IRON, NICKEL AND COBALT, DISSOLVING SAID METALLIC HALIDE IN A NON-AQUEOUS ORGANIC SOLVENT HAVING A HIGH SOLUBILITY FOR SAID METALLIC HALIDE, MIXING A CARBIDE POWDER IN THE FORMED SOLUTION, THE NON-AQUEOUS ORGANIC SOLVENT BEING FREE OF WATER TO PREVENT OXIDATION OF THE CARBIDE POWDER, EVAPORATING SAID SOLVENT TO RESULT IN A POWDER, PLACING SAID POWDER IN A REDUCING ATMOSPHERE, AND REDUCING SAID METALLIC HALIDE TO THE METAL THEREOF. 